全文获取类型
收费全文 | 3252篇 |
免费 | 97篇 |
国内免费 | 22篇 |
专业分类
化学 | 2038篇 |
晶体学 | 11篇 |
力学 | 145篇 |
数学 | 494篇 |
物理学 | 683篇 |
出版年
2024年 | 2篇 |
2023年 | 33篇 |
2022年 | 56篇 |
2021年 | 113篇 |
2020年 | 100篇 |
2019年 | 80篇 |
2018年 | 58篇 |
2017年 | 45篇 |
2016年 | 129篇 |
2015年 | 91篇 |
2014年 | 134篇 |
2013年 | 168篇 |
2012年 | 222篇 |
2011年 | 252篇 |
2010年 | 142篇 |
2009年 | 123篇 |
2008年 | 199篇 |
2007年 | 193篇 |
2006年 | 207篇 |
2005年 | 191篇 |
2004年 | 146篇 |
2003年 | 127篇 |
2002年 | 126篇 |
2001年 | 50篇 |
2000年 | 23篇 |
1999年 | 29篇 |
1998年 | 32篇 |
1997年 | 38篇 |
1996年 | 36篇 |
1995年 | 21篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 9篇 |
排序方式: 共有3371条查询结果,搜索用时 46 毫秒
191.
Vecchio Ciprioti Stefano Rotaru Andrei Blanco Ignazio Erceg Matko 《Journal of Thermal Analysis and Calorimetry》2020,142(5):1601-1604
Journal of Thermal Analysis and Calorimetry - 相似文献
192.
Annalisa Maruca Roberta Rocca Raffaella Catalano Francesco Mesiti Giosu Costa Delia Lanzillotta Alessandro Salatino Francesco Ortuso Francesco Trapasso Stefano Alcaro Anna Artese 《Molecules (Basel, Switzerland)》2020,25(23)
Mushrooms can be considered a valuable source of natural bioactive compounds with potential polypharmacological effects due to their proven antimicrobial, antiviral, antitumor, and antioxidant activities. In order to identify new potential anticancer compounds, an in-house chemical database of molecules extracted from both edible and non-edible fungal species was employed in a virtual screening against the isoform 7 of the Histone deacetylase (HDAC). This target is known to be implicated in different cancer processes, and in particular in both breast and ovarian tumors. In this work, we proposed the ibotenic acid as lead compound for the development of novel HDAC7 inhibitors, due to its antiproliferative activity in human breast cancer cells (MCF-7). These promising results represent the starting point for the discovery and the optimization of new HDAC7 inhibitors and highlight the interesting opportunity to apply the “drug repositioning” paradigm also to natural compounds deriving from mushrooms. 相似文献
193.
Giorgio Olivo Giorgio Capocasa Barbara Ticconi Osvaldo Lanzalunga Stefano Di Stefano Miquel Costas 《Angewandte Chemie (International ed. in English)》2020,59(31):12703-12708
Predictability is a key requirement to encompass late‐stage C?H functionalization in synthetic routes. However, prediction (and control) of reaction selectivity is usually challenging, especially for complex substrate structures and elusive transformations such as remote C(sp3)?H oxidation, as it requires distinguishing a specific C?H bond from many others with similar reactivity. Developed here is a strategy for predictable, remote C?H oxidation that entails substrate binding to a supramolecular Mn or Fe catalyst followed by elucidation of the conformation of the host‐guest adduct by NMR analysis. These analyses indicate which remote C?H bonds are suitably oriented for the oxidation before carrying out the reaction, enabling prediction of site selectivity. This strategy was applied to late‐stage C(sp3)?H oxidation of amino‐steroids at C15 (or C16) positions, with a selectivity tunable by modification of catalyst chirality and metal. 相似文献
194.
Dr. Elmar Kataev Daniel Wechsler Prof. Federico J. Williams Julia Köbl Dr. Natalia Tsud Dr. Stefano Franchi Prof. Hans-Peter Steinrück Dr. Ole Lytken 《Chemphyschem》2020,21(20):2293-2300
Thin-film growth of molecular systems is of interest for many applications, such as for instance organic electronics. In this study, we demonstrate how X-ray photoelectron spectroscopy (XPS) can be used to study the growth behavior of such molecular systems. In XPS, coverages are often calculated assuming a uniform thickness across a surface. This results in an error for rough films, and the magnitude of this error depends on the kinetic energy of the photoelectrons analyzed. We have used this kinetic-energy dependency to estimate the roughnesses of thin porphyrin films grown on rutile TiO2(110). We used two different molecules: cobalt (II) monocarboxyphenyl-10,15,20-triphenylporphyrin (CoMCTPP), with carboxylic-acid anchor groups, and cobalt (II) tetraphenylporphyrin (CoTPP), without anchor groups. We find CoMCTPP to grow as rough films at room temperature across the studied coverage range, whereas for CoTPP the first two layers remain smooth and even; depositing additional CoTPP results in rough films. Although, XPS is not a common technique for measuring roughness, it is fast and provides information of both roughness and thickness in one measurement. 相似文献
195.
Giovanni Ghigo Matteo Bonomo Achille Antenucci Chiara Reviglio Stefano Dughera 《Molecules (Basel, Switzerland)》2022,27(6)
Deep Eutectic Solvent (DES)-like mixtures, based on glycerol and different halide organic and inorganic salts, are successfully exploited as new media in copper-free halodediazoniation of arenediazonium salts. The reactions are carried out in absence of metal-based catalysts, at room temperature and in a short time. Pure target products are obtained without the need for chromatographic separation. The solvents are fully characterized, and a computational study is presented aiming to understand the reaction mechanism. 相似文献
196.
197.
Iacus Stefano Maria Santamaria Carlos Sermi Francesco Spyratos Spyros Tarchi Dario Vespe Michele 《Nonlinear dynamics》2020,101(3):1901-1919
Nonlinear Dynamics - Countries in Europe took different mobility containment measures to curb the spread of COVID-19. The European Commission asked mobile network operators to share on a... 相似文献
198.
The cationic bioxazoline Pd(II) complex 2 catalyzes the alternating copolymerization of carbon monoxide with styrene and 4-methylstyrene, respectively, to yield a highly isotactic optically active polymer at room temperature and low carbon monoxide pressure (1–4 atm). 相似文献
199.
Stefano Carli Wouter Dekeyser Reinart Coosemans Renaud Dejarnac Michael Komm Miglena Dimitrova Jiří Adámek Petra Bílková Petr Böhm 《等离子体物理论文集》2020,60(5-6):e201900155
Mean-field plasma edge transport codes such as SOLPS-ITER heavily rely on ad-hoc radial diffusion coefficients to approximately model anomalous transport. Such coefficients are experimentally determined and vary between different machines, and also depend on the operational regime and plasma location within the same device. Therefore, to match experimental data the modeller is required to manually tune several free parameters in expensive simulations, and the code's predictive capabilities are significantly downgraded. As a solution, a new model has been developed for SOLPS-ITER, solving an additional transport equation for the turbulent kinetic energy k, derived by consistently time-averaging the Braginskii equations, and including a diffusive closure for the anomalous particle flux. This closure model relates the anomalous diffusion coefficient to the local k value. The resulting equation structure and its closure are inspired by TOKAM2D isothermal interchange turbulence simulation results. Within this model, fewer and hopefully more universal free parameters are retained, thus improving the code's predictive capabilities. The new model has been tested on a COMPASS case for which upstream plasma profiles were available. Experimental data and a reference solution, obtained by matching the profiles through manual tuning of radial diffusivities, have been used to estimate the parameters of our new transport model. A ballooned particle diffusivity profile is retrieved by the new radial transport model, thanks to the proposed interchange drive. The obtained upstream profiles qualitatively agree with the experiment and prove the new model is a promising first attempt to be further refined. 相似文献
200.
The optimum performance of an optical oxygen sensor based on polysulfone (PSF)/[Ru(II)-Tris(4,7-diphenyl-1,10-phenanthroline)] octylsulfonate (Ru(dpp)OS) was checked by carefully tuning the parameters affecting the membrane preparation. In particular, membranes having thickness ranging between 0.2 and 8.0 μm with various luminophore concentrations were prepared by dip-coating and tested. The membrane thickness was controlled by tuning the solution viscosity, and was measured both by secondary ion mass spectrometry (SIMS) and by visible spectroscopy (Vis). Luminescence-quenching-based calibration was a single value of the Stern-Volmer constant (K′SV) for membranes containing up to 20 mmol Ru(dpp) g−1 PSF (1.35 μm average thickness). The K′SV value decreased for larger concentration. The highest sensitivity was obtained with membrane thickness around 1.6 μm, having a response time close to 1 s. Thicker membranes exhibited an emission saturation effect and were characterized by longer response time. The K′SV behavior was interpreted on the basis of a mathematical approach accounting for the contribution of luminescence lifetime (τ0), oxygen diffusion coefficient (DO2) and oxygen solubility inside the membrane (sO2) establishing the role of all of them and allowing their experimental determination. Moreover, a simple experimental way to estimate K′SV without needing calibration was proposed. It was based either on the light emission asymmetry or on the percent variation of light emission on passing from pure nitrogen to pure oxygen. 相似文献